1. Industrial Field of the Invention
The present invention relates to a method of laser-marking semiconductor devices, and, more particularly, to a method of marking the resin surface of a resin sealed type of semiconductor devices by a YAG laser.
2. Prior Art
FIG. 1 is a schematic structural view of a conventional YAG laser-marking device for use in a marking method . Referring to this drawing, laser beam 2, for example, pulsed laser beam, is generated by a laser beam generating device 1. The thus-generated laser beam 2 is introduced, by means of mirrors 3, to a laser beam rectifying portion 4 wherein the beam is rectified and made substantially the same size as that of a mask 5. Mask 5 has a surface thereof engraved with a mark such as characters. The thus-rectified laser beam 2 takes the shape of this character or the like by being passed through this mask 5. The laser beam 2 is applied to the surface of a resin, for example, an epoxy resin, which seals a semiconductor device 8 so that the surface of the resin is engraved with the mark.
The conventional laser marking method is performed as described above wherein the pulse width of the laser beam 2 is 0.2 to several ms (millisecond), the energy density is 3 to 60 J/cm.sup.2, and the diameter of the beam is several mm to ten and several mm. These laser conditions are values for the semiconductor devices.
In the above described type of laser-marking method, the amount of cinders generating by burning the sealing resin on the semiconductor device with the engraving laser beam is too large. Therefore, the engraved character can be clearly seen due to the above-described cinders. A problem is caused since cinders needs to be removed, such as by wiping the resin cinders with a cloth wetted with alcohol.